Because your great aunt will diligently learn how to take photos and later send them to you, but then some clever young designer goes and moves the buttons arou

Because your great aunt will diligently learn how to take photos and later send them to you, but then some clever young designer goes and moves the buttons around and adds some "smart" reorganization, and now she can't find that photo she took of that weird-looking spot on her basement wall the other day, and when she stumbles upon it again, the process you painstakingly trained her on to send it to you no longer works. So her interest in re-learning how to do this is diminished, because she rightfully no longer trusts that it won't change yet again. Constantly shifting UIs undermine user trust, especially for users who are further from peak learning years. My three year old, of course, worked out how to navigate around my photos despite my never handing him my phone, and even discovered a feature I didn't know existed. Adaptation is often slower as you age - I can see this a bit in myself now that I'm past 40. I have to more consciously learn new things than I did 20 years ago.